A Cancer-Quashing Microbe Emerges from the Deep

While we often think of them as life-threatening, bacteria are so numerous and so varied that these microbes have saved countless people from death. Through several decades in the 20th century, scientists harnessed bacteria to produce natural but specific chemical compounds that could be used to prevent and/or treat disease, particularly the useful class called Actinomycetes. The more exotic the bacteria's habitat, the more specific these chemicals turned out to be. But it's hard to find new bacteria. Oceanographer Paul Jensen and chemist William Fenical teamed up to look into the ocean depths for marine bacteria that were different from their landlocked cousins, in order to study their potentially useful chemical talents.

At the time, says Fenical, the consensus among pharmaceutical microbiologists was that actinomycetes lived only on land, and therefore “nothing was important in the oceans.” But Fenical suspected that a sampling bias drove that conclusion, and in June 1989, he and Jensen traveled to the Bahamas to see for themselves, collecting vials of ocean-floor sediment from 15 different locations at depths of up to 33 meters. Back at the lab, it didn’t take long for the two scientists to prove the naysayers wrong. When they cultured their samples, they found 289 separate actinomycete colonies. Some of these bacteria, members of a new genus that they later named Salinispora, had never been documented on land. Moreover, they were most abundant in the deeper samples, suggesting that they hadn’t simply washed into the ocean with terrestrial runoff. And then there was the kicker: Salinispora grew only in salt water.

Working with a team of colleagues, Jensen eventually identified two different species of Salinispora bacteria from the Bahamian samples, both of which produced unique active compounds. One of these species, S. tropica, made a molecule that would change the course of their careers. When Fenical tested it on a line of difficult-to-kill human colon cancer cells, the compound passed with flying colors. He then sent it to labs at the National Cancer Institute to be tested against a panel of 60 different cancer cells. The results were exactly what Jensen and Fenical wanted to see: the compound, which they named salinosporamide A, was especially active against some cancer cell lines, but not others.

“You want that selectivity, because if it kills all cancer cells equally, then it’s probably also going to equally kill noncancerous cells,” Jensen explains. It seemed they had the makings of a viable drug on their hands: a compound that could target a tumor without killing the person it afflicted.

Read how salinosporamide A, also called marizomib, went from a bacterial product to a life-saving medicine at Hakai magazine. The article is also a look into how networks of scientists in the field, the lab, and in patient care have to work together to advance medical science. -via Real Clear Science 

#medicine #bacteria #cancer

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